Oil-impregnated, fibrous, cellulose wicking materials, which can be injected under pressure into bearing reservoirs, without separation of the lubricating oil and the fibrous wicking material, are well known in the art. Abel, in U.S. Pat. No. 2,966,459, taught injectable, oil-impregnated, chemically pulped, fibrous, cellulose wicking materials, consisting of pulverized cellulose fibers and a mixture of paper-containing fibers of wood and cotton. These cellulose fibers are used in varying amounts. They can be injected into bearing cavities and used in fractional horsepower motor bearings and other sleeve bearings.
Berkeley, in U.S. Pat. No. 3,214,375, taught injectable, oil retaining, fibrous wicking materials, consisting of cellulose fibers, completely film coated with an oil resistant polyamide polymer, which could be mixed with nylon or graphite fibers, to provide faster oil release to bearing surfaces.
These materials, however, when used in highly loaded bearings operating at elevated temperatures, tend not to release the oil fast enough to insure complete, protective lubrication. Abel, in U.S. Pat. No. 3,466,244, attempted to provide faster oil release materials, by using all cotton linter fibers, as the injectable, oil-impregnated wicking material.
Even though advances have been made, problems still remain in lubricating highly loaded bearings operating at elevated temperatures, in that wicking materials are needed which will provide even faster flow rates than those taught in the art. The ideal wicking material for fractional horsepower motor bearings should exhibit the highest possible flow rate, at any given oil content, and even more importantly, it should deliver the maximum amount of oil to the bearing surface i.e. at least about 40 weight percent before oil flow essentially stops. The best prior art wicking materials deliver only about 30 weight percent of the contained oil.
Obviously, a highly absorbant wicking material, which tenaciously holds onto the oil absorbed therein, and which will not function to deliver most of its contained oil, is of little merit in the important function of supplying lubricant to a bearing.
What is needed is a new and improved wicking material that will provide a more liberal quantity of oil to the surface to be lubricated than the prior art materials, and which will continue to supply the oil for a longer time period, as shown by the increased amount of total oil released.